No smoking rear tyres or a V8, but world's fastest hot-hatch is more than worthy of the AMG badge.

Pros and Cons

Pros

Taut handling

Engine performance

Tremendous grip and traction

Exhaust sound

Great brakes

Highly specified and high-quality cabin

Cons

Auto gearbox can disobey paddle shift commands

Urban ride still to be tested

More rear-biased AWD set-up would be even better

4cyl doesn't sound as good as M135i's 6cyl

No V8. No rear-wheel drive. Hatchback. The Mercedes-Benz A45 AMG is bordering on the radical for the German brand’s fabled performance division.

Aufrecht Melcher Grossapach, as it’s otherwise not so well known, has been producing rear-tyre-shredding Mercedes muscle sedans and sports cars since the late 1960s (and officially since 1990).

Mercedes, though, is in the middle of an aggressive sales expansion with a whole new range of affordable, compact cars targeting younger buyers than the traditional Benz owner – so the company has applied the AMG badge to its smallest model, the A-Class, for the first time.

Starting at $74,900 before on-road costs, the Mercedes-Benz A45 AMG costs less than half the price of what was previously the most affordable AMG model, the C63 AMG sedan.

The A45 has half the number the cylinders, though we should have guessed AMG wasn’t going to produce any ordinary engine for its first four-cylinder.

With 265kW produced from the 2.0-litre turbo, the A45 AMG’s engine is the most powerful series production four-cylinder in the world. With 133kW per litre of capacity, its specific output surpasses that of a Porsche 911 GT2.

Even AMG engineers aren’t brave enough to try putting all that power through the front wheels alone, so the A-Class for its hottest form switches from front-drive to all-wheel drive.

It’s an on-demand set-up that is front drive in normal driving but capable of sending up to 50 per cent of the engine’s torque to the rear wheels when required.

Such an occasion would be off-the-line acceleration, and the 0-100km/h result for the Mercedes-Benz A45 AMG is 4.6 seconds (though it’s been clocked faster).

That’s three-tenths quicker than its closest current rival, the $64,900 BMW M135i with 235kW and an equal 450Nm of torque of 450Nm.

Think of the transition between the six-cylinder VW Golf R32 to the four-cylinder Golf R, or the BMW 330i six to 328i four, and there are plenty of examples showing how many manufacturers have struggled to make turbo fours sound as good as six-cylinders.

And while the M135i’s engine entertains with induction noise and a snarling soundtrack, the A45 is different to other AMGs in that its aural show owes more to its variation of exhaust notes than what you can hear under the bonnet besides a little chirrup from the turbo.

But terrific those notes are. Lift off the throttle and the A45’s sports exhaust – an option elsewhere in the world but standard in Australia – burbles and crackles on the over-run, while upshifts in the transmission’s Sports mode are accompanied by what can be best described as mini thunderclaps.

There’s just a hint of turbo lag if you drive the A45 AMG in the Comfort gearbox mode but it disappears entirely in Sport.

It’s an engine that’s easy to drive at low speeds, but let it rip and there’s an unrelenting surge towards the 6200rpm redline via a thumping mid-range.

The tachometer needle swings with such enthusiasm that it’s easy to find yourself forgetting to upshift quickly enough – if using the paddleshift levers and Manual mode – and find yourself bumping into the limiter.

Barrel into a series of corners and the Mercedes-Benz A45 AMG expands its list of impressive attributes to mark it out as a brilliant hot-hatch.

Super-tight body control keeps the baby AMG terrifically planted over bumpy country roads, intimately bolstered bucket seats keep the driver secured, and the A45’s balletic balance through direction changes enforces this Mercedes as a car capable of a thrillingly fluid drive.

There’s no torque steer when jumping enthusiastically on the throttle out of corners, either – just tremendous levels of traction that allows you to get on the power early, as well as huge levels of grip from the Dunlop Maxx Sport 235/35s fitted to our test cars (Continental rubber will also be available).

On the road the A45 AMG can carry such high cornering speeds without threatening to understeer, though the AWD set-up still feels more like a front-wheel-drive rather than rear-wheel-biased car so the only missing piece of the fun factor jigsaw is the ability to play around more with the hatch’s back end.

The steering is a bit stiff around the straight-ahead so you can find yourself making fussy incremental movements of the wheel on a straight road, but it offers plenty of satisfaction with just-right weighting, accuracy and genuine feel.

The dual-clutch auto brings quick shifts, though as we experienced with the gearbox in the regular (A-Class-based) CLA overseas earlier this year the driver's downshifts via the paddle shift levers can be annoyingly ignored at times.

On the racerack (we also tested at Phillip Island), the A45 AMG doesn’t disappoint. Understeer that is near-impossible to find on the road reveals itself at unlimited speeds, but the hatch’s tremendous grip levels and that responsive front end remain impressive constants. The (big) brakes are superb – strong, easy to modulate and fade resistant.

It’s still not an AMG where you can play around with the rear end much in slower corners, but there is mid-corner adjustability via the throttle in fast challenging corners – such as PI’s Southern Loop and Lukey Heights – to tuck the nose into the apex if the A45 does start to push wide.

The optional Performance suspension ($1990) is definitely a box worth ticking if you do plan to attend some track days. A so-equipped A45 brings 20 per cent stiffer springs and dampers sits noticeably flatter through corners than one of the standard suspension.

We didn’t get to try the Performance suspension on the road, though we can tell you the standard suspension on country roads is firm yet forgiving enough that it avoids the low-speed harshness that can be experienced in the C63.

If you want more downforce to suck your A45 AMG to the ground, a $1990 Aerodynamics Package (pictured above) brings a larger front splitter, front flics and a prominent rear wing. Mercedes says the package applies another 40kg of downforce at 250km/h.

In Australia, though, that’s about as useful as the Drivers’ Package that’s also standard and lifts the A45’s top speed to 270km/h.

Still, there’s no denying Mercedes-Benz has been as generous with the A45 AMG’s equipment as other A-Classes.

There's a high-quality feel to the cabin, too, with expensive-feeling materials including the artificial carbon fibre weave on the dash. The use of red for stitching, parts of the seats, inner vent surrounds and seat belts contribute to an appropriately sporty design theme.

If practicality still has to be a factor in the A45 buying process, the A-Class offers good legroom in the back seats (though realistically only for two adults, and you wouldn't want the front occupants to be too tall), storage options are plentiful, though the boot is on the small side even for a hatch.

So, as we said at the start, this is an AMG with a difference. We need to try it as a daily driver to see whether it's easy to live with in the commuting grind, but on the open road and on the track, even if there's no billowing smoke from the rear tyres, the Mercedes-Benz A45 AMG serves up the kind of agility, performance and overall sense of slight deviousness expected from that famous tri-letter badge.